Abstract Methamphetamine (MA) use among men who have sex with men (MSM) is associated with increased rates of HIV prevalence and transmission, as well as substandard advancement along the HIV Prevention and Care Continua. MA use among MSM is deeply integrated into socio-sexual networks including the use of smartphone applications (?app?) and websites to find sexual partners. Given the growth of mobile health technology, it is no longer necessary or reasonable to limit MA treatment options to physical sites, clustered in urban areas, and administered using generic, non-tailored content. The project builds upon the established efficacy of our manualized MA-abuse treatment intervention, ?Getting Off: A Behavioral Treatment Intervention for Gay and Bisexual Male Methamphetamine Users,? and the highly promising findings from our successful Stage I proof-of-concept study, to complete translation of Getting Off into a cross-platform (iOS and Android) app and assess the app?s efficacy and non-inferiority in a scientifically rigorous randomized trial. The Getting Off app, like the group-based intervention before it, will use the principles of Cognitive Behavioral Theory and Stages of Change to help MSM reduce or eliminate MA use and HIV sexual risk behaviors, and increase advancement along the HIV Prevention or Care Continuum (including uptake of HIV testing, pre-, and post- exposure prophylaxis [PEP/PrEP] and PrEP adherence and persistence for those who are HIV negative; ART uptake and adherence for those who are HIV positive). This project will 1) refine and enhance the first 8 sessions of the Getting Off MA-abuse treatment intervention developed in Stage I based on feasibility pilot test user feedback, 2) conduct formative research to develop the remaining 16 sessions of the Getting Off MA- abuse treatment intervention into a cross-platform computerized mobile app targeted to reduce MA use and HIV sexual risk behaviors, and increase advancement along the HIV Prevention or Care Continuum, and 3) conduct a RCT to evaluate reductions of MA use and HIV sexual risk behaviors, and increased advancement along the HIV Prevention or Care Continuum, using three approaches: a) Efficacy Trial ? a two-arm RCT to determine intervention effects through comparison of the Immediate Delivery (ID; n=150) and Delayed Delivery (DD; n=150) arms; b) Efficacy Trial ? an observed treatment effects analysis to compare pre/post data from the pooled ID and DD conditions (N=300); and, c) Non-inferiority Trial ? a two-arm historical matched comparison design to evaluate the outcomes of the Getting Off app (ID + DD; N=300) relative to a matched sample of participants having previously attended the brick-and-mortar group-based Getting Off intervention (N~600; total N=900). The RCT uses repeated measures to assess participants at baseline, 1-, 2- (DD condition only), 3-, 6-, and 9-month follow-up. This study could have significant public health impact by greatly expanding access to effective, affordable, private, culturally competent and highly scalable MA treatment to this very high-risk population.